A fiercely intelligent man with deeply conservative, nationalistic and aggressive views about American foreign policy, Mr. Bolton may bring more consistency and predictability to President Trump’s foreign policy, many suggest. But others worry that his hawkish views on Iran and North Korea, among others, may goad Mr. Trump into seeking military solutions to diplomatic problems.

…and kill us all.

Unless, of course, Trump gets bored with him as quickly as he gets bored with most people and trades him in for a different Fox “personality.”

“Bolton is relentless, intelligent and effective,” said François Heisbourg of the International Institute for Strategic Studies, who as a French military analyst dealt with Mr. Bolton during the administration of George W. Bush. “But he’s not a neoconservative and has no interest in democracy promotion. He is a man of the Trumpian world — no allies, no multilateralism.”

Just all “Us First” all the time.

The appointment of Mr. Bolton has set teeth on edge in Asia, where American allies are highly anxious about a developing nuclear crisis that appears all but inevitable. Mr. Bolton, Mr. Pompeo and Mr. Trump all say that North Korea could face pre-emptive warfare if it does not agree to dismantle its nuclear weapons.

Set teeth on edge? That’s a weird metaphor. Anyway, that one’s the biggest terrifier.

Lee Byong-chul, senior fellow at the Institute for Peace and Cooperation in Seoul, said that South Korea must now manage its “very bad chemistry” with Mr. Bolton, “who is all about sticks.”

Mr. Bolton has derided South Korea for trying to play peacemaker with Pyongyang, saying the South was “like putty in North Korea’s hands.”

“We will have to see if Bolton opens his mouth and launches his verbal attacks against the North,” Mr. Lee said. “That will give North Korea an excuse to step away from its summit proposal. The Trump-Bolton team then will ramp up pressure. And we will hear more talk about a pre-emptive strike and see tensions rising again on the Korean Peninsula.”

Others thought he might temper his words, but China would still worry about Mr. Bolton having Mr. Trump’s ear, said Chen Dingding, a professor of international relations at Jinan University in Guangzhou, China.

“He’s a hard-liner, not just toward China but to the whole world,” Mr. Chen said. “North Korea, Iran, the European Union, the United Nations — every side — it’s not just China. But he does represent a worldview of the Trump administration, one of ‘America First’ and unilateralism over multilateralism. I think the whole world should be concerned, not just Asia.”